Scalable packet processing systems and methods

ABSTRACT

A data processing architecture includes multiple processors connected in series between a load balancer and reorder logic. The load balancer is configured to receive data and distribute the data across the processors. Appropriate ones of the processors are configured to process the data. The reorder logic is configured to receive the data processed by the processors, reorder the data, and output the reordered data.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 12/130,766, filed May 30, 2008 (now issued as U.S. Pat. No. 8,234,653), which is a continuation of U.S. patent application Ser. No. 10/382,863, filed Mar. 7, 2003 (now issued as U.S. Pat. No. 7,395,538), the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to data processing and, more particularly, to scalable packet processing systems and methods.

2. Description of Related Art

Programmable processors can be used to create highly flexible packet processing applications. Often the performance requirements of these applications exceed the capacity of a single programmable processor. Using multiple programmable processors to achieve higher performance is challenging, however. Various problems must be solved to achieve an architecture that is both highly flexible and high performing. These problems include physical connection of multiple processors to a single stream of packets; classifying, managing, balancing, and distributing the flow of packet processing work through the available processing resources; maintaining packet ordering when packets fan out and flow through different resources; and ensuring that single processing elements or engines within processors have enough program space to run the entire processing application.

There are many types of packet processing architectures. One type of processing architecture attempts to achieve high performance by creating a pipeline of processing stages. FIG. 1 is a diagram of a pipelined packet processing architecture. The pipelined architecture includes multiple processing stages 110-1 through 110-4 (collectively referred to as processing stages 110), connected in series, that act together to perform a packet processing application. Each of stages 110 performs part of the application.

When a packet arrives at a processing stage, such as processing stage 110-2, processing stage 110-2 performs a portion of the application to generate intermediate results. Processing stage 110-2 then outputs the packet and the intermediate results to the next stage (i.e., processing stage 110-3) where processing continues. Because intermediate results are transmitted in addition to the packet, the bandwidth required into and out of processing stages 110 must be greater than the bandwidth of the packet itself.

With such an architecture, high performance can be achieved by adding additional processing stages 110. When this happens, however, the application functions must be redistributed over processing stages 110. It is important to balance the application functions performed by each of processing stages 110. If one stage is given much more work than the other stages, then that stage may become overloaded while other stages have unused capacity. In this case, the overloaded stage may become a bottleneck that limits the performance of the entire pipeline.

The distribution of application functions across a pipeline is a very difficult task. It becomes even more difficult as the number of processing stages 110 increases. Also, if the application needs to be changed to add new features, then the entire application may need to be redistributed across the pipeline. As a result, the pipeline architecture is not flexible.

Another type of processing architecture attempts to achieve high performance by connecting packet processors in parallel. FIG. 2 is a diagram of a parallel packet processing architecture. The parallel packet processing architecture includes packet processors 210-1 through 210-4 (collectively referred to as processors 210) connected between a sprayer 220 and a desprayer 230. Unlike the pipelined packet processing architecture, each of processors 210 in the parallel processing architecture includes the entire packet processing application. In other words, each of processors 210 performs the same application functions.

Sprayer 220 receives packets and load balances them across processors 210. Processors 210 receive the packets, process them, and send them to desprayer 230. Because the processing time for processing packets by processors 210 may vary, the packets may become out of order relative to the order in which they were received by sprayer 220. As a result, desprayer 230 reorders the packets to the order in which they were received by sprayer 220.

This parallel processing architecture is less scalable because the functions of sprayer 220 and desprayer 230 become increasingly harder to build as the number of processors 210 increases. Also, a lot of physical connections are required to connect sprayer 220 and desprayer 230 to processors 210, making it difficult to design and build. As a result, the parallel architecture has limited performance.

Accordingly, there is a need for a scalable packet processing architecture that can flexibly connect multiple processors while supporting a dynamic set of applications and features.

SUMMARY OF THE INVENTION

Systems and methods consistent with the principles of the invention address this and other needs by providing a scalable packet processing architecture that combines the benefits of both the pipelined and parallel architectures without their shortcomings.

One aspect consistent with the principles of the invention includes a data processing architecture that includes multiple processors connected in series between a load balancer and reorder logic. The load balancer is configured to receive data and distribute the data across the processors. Appropriate ones of the processors are configured to process the data. The reorder logic is configured to receive the data processed by the processors, reorder the data, and output the reordered data.

According to another aspect consistent with the principles of the invention, a parallel pipeline system is provided. The system includes multiple pipelines connected between a load balancer and reorder logic. Each of the pipelines includes multiple processors connected in series that are configured to process data. The load balancer is configured to receive data and distribute the data across the pipelines for processing. The reorder logic is configured to receive the data processed by the processors in the pipelines, reorder the data, and output the reordered data.

According to yet another aspect consistent with the principles of the invention, a processor of multiple processors connected in one or more pipelines is provided. The processor includes multiple resources arranged in resource groups and connected between a receiver and a transmitter. The receiver is configured to receive data, determine whether the data is intended for one of the resource groups, forward the data to another one of the processors via a bypass path to the transmitter when the data is not intended for one of the resource groups, and distribute the data to one of the resources in one of the resource groups when the data is intended for one of the resource groups.

According to a further aspect consistent with the principles of the invention, a load balancer connects to multiple processors arranged in one or more pipelines. The load balancer includes a classifier, multiple queues, and binding logic. The classifier is configured to receive data. The queues are configured to store the data based on a type of the data. The binding logic is configured to identify ones of the processors to process the data stored in the queues based on states of the processors and distribute the data to the identified processors.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings,

FIG. 1 is a block diagram of a pipelined packet processing architecture;

FIG. 2 is a block diagram of a parallel packet processing architecture;

FIG. 3 is an exemplary diagram of scalable packet processing system according to an implementation consistent with the principles of the invention;

FIG. 4 is an exemplary diagram of a processor of FIG. 3 according to an implementation consistent with the principles of the invention;

FIG. 5 is an exemplary diagram of the load balancer of FIG. 3 according to an implementation consistent with the principles of the invention;

FIG. 6 is an exemplary diagram of the reorder logic of FIG. 3 according to an implementation consistent with the principles of the invention;

FIG. 7 is an exemplary diagram of the buffer of FIG. 6 according to an implementation consistent with the principles of the invention;

FIG. 8 is a flowchart of exemplary processing by the packet processing system of FIG. 3 according to an implementation consistent with the principles of the invention;

FIG. 9 is a block diagram illustrating an exemplary multiple pipeline packet processing system consistent with the principles of the invention; and

FIG. 10 is an exemplary diagram of the load balancer of FIG. 9 according to an implementation consistent with the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents.

Systems and methods consistent with principles of the invention provide a scalable packet processing system which is flexible in the addition of or changes to the number of processors, the application functions performed, and the features provided. The systems and methods accomplish this, at least in part, via a processing architecture that appears like a pipelined architecture, but performs like a parallel architecture.

While the description to follow will focus on the processing of packets, systems and methods consistent with the principles of the invention are not so limited. In fact, systems and methods consistent with the principles of the invention may operate upon any form of data, including packet and non-packet data.

Exemplary Single Pipeline System Overview

FIG. 3 is a block diagram illustrating an exemplary packet processing system 300 consistent with the principles of the invention. In one implementation, system 300 is provided within a network device, such as a router, switch, or server. System 300 may include processors 310-1 through 310-N, where N≧2 (collectively referred to as processors 310), connected as a pipeline (in series) between load balancer 320 and reorder logic 330.

The role of load balancer 320 is to coarsely manage packet processing resources of processors 310 by directing individual packets to a resource group within one of processors 310. Each of processors 310 more finely manages its own local resource groups and further directs packets to individual processing resources within that processor. This hierarchical management of processing resources means that load balancer 320 need not have knowledge of all of the individual processing resources, but only knows about groups of resources which share a common function. In many cases, this common function might be an entire packet forwarding application.

Processors 310 may include processor chips on a circuit board or processor elements of an application specific integrated circuit. Each of processors 310 may comprise one or more processing elements. Processors 310 may have a bus bandwidth capable of carrying packets at a high rate. Individual processors 310 may, however, not actually be capable of any significant packet processing of the packets at that rate. Processors 310 may connect in a physical pipeline, though, as will be described below, they act as if they were connected in parallel.

Load balancer 320 may load balance packets across all processors 310. In implementations consistent with the principles of the invention, processors 310 may include a bypass mechanism, such that if a packet arrives at a processor that is not intended for a resource local to that processor, it is transmitted out of the processor, utilizing little or no resource within that processor. This provides for physical simplicity without constraining flexibility. Instead of distributing the application across multiple processors as in the pipelined approach, each of processors 310 may run the entire application. The packets will be balanced across processors 310.

Because packets may require variable packet processing times, packets may pass each other as they move through processors 310. This means that packets may complete processing in a different order than they arrived. In many instances, it is important for packets to be sent out in the same order in which they were received. Reorder logic 330, in conjunction with load balancer 320, can order the packets back to the original order in which they were received. In one implementation, load balancer 320 tags each packet with a sequence number that can later be used by reorder logic 330 to reorder the packets. Reorder logic 330 may return sequence numbers for subsequent use by load balancer 320.

Reorder logic 330 may aid load balancer 320 in balancing the distribution of packets across processors 310. For example, reorder logic 330 may obtain information regarding the state of processors 310 and provide this information to load balancer 320.

Sometimes packets may require processing by more than one of processors 310. Reorder logic 330 may identify these packets based on information associated with the packets and send the packets back to load balancer 320 for transmission to other processors 310.

Exemplary Processor Configuration

FIG. 4 is an exemplary diagram of one of processors 310, such as processor 310-1, according to an implementation consistent with the principles of the invention. The other processors 310 may be configured similarly. Processor 310-1 may include a number of resources 410-1 through 410-M, where M≧1 (collectively referred to as resources 410), connected between receiver 420 and transmitter 430. Receiver 420 and transmitter 430 may further connect to each other via bypass path 440 and redirect path 450.

Resources 410 may include processing engines that perform certain packet processing functions. Each of resources 410 may include a physical resource or a virtual resource, or both. Ideally, each of resources 410 performs the entire set of processing functions. In practice, however, processor size may limit the size of the program that can be run on any given one of resources 410. In this case, each of resources 410 may perform a certain set of processing functions.

Resources 410 may be grouped into resource groups 412-1 through 412-P, where P≧1 (collectively referred to as resource groups 412), based on the particular processing functions they perform. All resources 410 within one of resource groups 412 may perform the same processing functions. For example, resources 410 within one of resource groups 412 may perform Ethernet-related functions, while resources 410 within another one of resource groups 412 may perform ATM-related functions.

Receiver 420 may include logic that determines whether a received packet should be sent to a local resource (e.g., one of resources 410) or bypassed. Based on information included with or within the packet (e.g., a processor identifier and/or a resource group identifier), receiver 420 may identify one of resource groups 412 to process the packet. In this case, receiver 420 may assign the packet to one of resources 410 within the identified one of resource groups 412 in a manner to balance the number of packets (or amount of work or load) given to any one of resources 410. Receiver 420 may maintain information regarding the current load of its resources 410 so that it can balance the number of packets given to any one of resources 410 in an intelligent manner.

Alternatively, receiver 420 may determine that a packet is a “bypass packet” that is not intended for any of its resources 410. It may be important that the amount of effort required for receiver 420 to identify a bypass packet be minimal. When receiver 420 identifies a bypass packet, receiver 420 transmits the packet to transmitter 430 via bypass path 440. Processor 310-1 may be able to pass packets (via its bypass path 440) at full line rate.

Transmitter 430 may include logic that transmits packets from processor 310-1 to processor 310-2. Transmitter 430 of processor 310-N may transmit packets to reorder logic 330. Transmitter 430 may also redirect packets back to receiver 420 via redirect path 450. For example, a packet may require execution by more than one resource 410 within processor 310-1. In this case, transmitter 430 may redirect the packet to receiver 420 instead of sending the packet out of processor 310-1. Transmitter 430 may identify these packets based on information provided by resources 410. Receiver 420 may then send the packet to another one of resource groups 412 within processor 310-1.

A packet may also require execution by a resource 410 of another one of processors 310. In this case, resource 410 may mark the packet in some manner to indicate that it should be returned to load balancer 320 for transmission to another one of processors 410.

Exemplary Load Balancer Configuration

FIG. 5 is an exemplary diagram of load balancer 320 according to an implementation consistent with the principles of the invention. Load balancer 320 may include a classifier 510, processing queues 520-1 through 520-S, where S≧1 (collectively referred to as queues 520), and binding logic 530.

Classifier 510 may include logic that processes received packets to identify which of processing queues 520 to place the packets. Classifier 510 may make this identification based on one or more fields in the packets, information associated with the packets, or both. In other implementations, classifier 510 may use other information in identifying queues 520 to receive the packets. If classifier 510 determines that a packet is dependent (i.e., the packet requires processing by more than one resource group 412 (FIG. 4), as opposed to an independent packet that requires processing by only one resource group 412), then classifier 510 may optionally place the packet in one of queues 520 dedicated to dependent packets.

Processing queues 520 may include buffers associated with different types of packets to be processed. In implementations consistent with the principles of the invention, queues 520 may not directly relate to processors 310, but instead to the types of packets that processors 310 may process. For example, queues 520 may include buffers for multicast packets, dependent packets, Ethernet packets, and ATM packets.

Binding logic 530 may include logic that associates the packets in queues 520 with resource groups 412 (labeled as resource groups RG1-RGT) of processors 310. Binding logic 530 may include bindings from queues 520 to resource groups RG1-RGT that identify resource groups 412 that are capable of processing the packets. For example, a binding may exist between queue 520-1 and resource groups RG1 and RG2. This means that packets in queue 520-1 may be sent to either resource group RG1 or resource group RG2. The resource groups may physically reside within one or more processors 310.

Binding logic 530 may balance the distribution of packets across the associated resource groups. A particular packet may be assigned to more than one resource group (e.g., a packet from queue 520-3 may be assigned to resource group RG3 or RG4). In this case, binding logic 530 may use state information in making its assignment. Binding logic 530 may receive the state information from reorder logic 330 (FIG. 3). The state information may identify the general state of resource groups 412.

Binding logic 530 may send certain information along with packets that it outputs to processors 310. The information may be appended to the packets or sent in parallel with the packets. The information associated with a packet may include a processor identifier that identifies one of processors 310 to operate upon the packet. The information may also include a resource group identifier that identifies the particular resource group 412 to process the packet. The information may further include a sequence number that is used by reorder logic 330 to reorder packets that it receives to the order in which the packets were received by load balancer 320.

Exemplary Reorder Logic Configuration

FIG. 6 is an exemplary diagram of reorder logic 330 according to an implementation consistent with the principles of the invention. Reorder logic 330 may include receiver 610, buffer 620, and transmitter 630. Receiver 610 may include logic to process packets received from processor 310-N and store them in buffer 620. Receiver 610 may also return state information to load balancer 320 for packets it receives. The state information may indicate that the resource group that processed the packet is available to process another packet. As described above, load balancer 320 may use the state information when balancing the number of packets sent to each of resource groups 412.

Buffer 620 may store the packets based on their associated sequence numbers. Load balancer 320 may assign sequence numbers to packets that accompany the packets during processing by processors 310.

FIG. 7 is an exemplary diagram of buffer 620 according to an implementation consistent with the principles of the invention. Buffer 620 may include multiple storage locations that are addressable using the sequence number. When receiver 610 writes a packet to buffer 620, receiver 610 writes the packet to the storage location corresponding to the packet's sequence number. For example, when receiver 610 receives the packet associated with sequence number 2, receiver 610 writes the packet to buffer 620 at the storage location associated with sequence number 2.

Returning to FIG. 6, transmitter 630 may include logic that reads packets from buffer 620. Transmitter 630 may read the packets in order based on their sequence numbers. Transmitter 630 may wait for packets with earlier sequence numbers before reading packets with later sequence numbers. For throughput purposes, transmitter 630 may wait a predetermined amount of time for arrival of the packets with earlier sequence numbers. If this time period expires, transmitter 630 may begin reading the packets with the later sequence numbers and drop any of the packets with the earlier sequence numbers if they subsequently arrive.

When transmitter 630 reads a packet from buffer 620, transmitter 630 may determine whether the packet is to be transmitted from system 300 or sent back to load balancer 320 for further processing. Transmitter 630 may use information included with the packet in determining whether the packet requires further processing by system 300. For example, when a packet is processed by a processor 310, processor 310 may determine that the packet requires additional processing by another processor (or resource group). In this case, processor 310 may include instructions with the packet that instruct reorder logic 330 to send the packet to load balancer 320 for further processing. Transmitter 630 may use this information to redirect a packet back to load balancer 320.

When transmitter 630 reads a packet from buffer 620, transmitter 630 may return the sequence number associated with the packet to load balancer 320. Load balancer 320 may reuse the sequence number at the appropriate time.

Exemplary Processing for Single Pipeline System

FIG. 8 is a flowchart of exemplary processing by packet processing system 300 according to an implementation consistent with the principles of the invention. Processing may begin with load balancer 320 receiving one or more packets (act 810). Load balancer 320 may analyze the packets to load balance them across resource groups 412 within processors 310 (act 820). For example, load balancer 320 may use information within the packets (e.g., various packet fields) and information regarding the state of resource groups 412 (e.g., state information) to identify the particular resource groups 412 to which to send the packets.

Load balancer 320 may associate certain information with the packets to aid in later processing of the packets. For example, load balancer 320 may assign processor identifier and/or resource group identifier information to a packet to aid in transmission of the packet to the correct one of resource groups 412. Load balancer 320 may also assign sequence numbers to packets to help reorder logic 330 reorder the packets prior to transmission.

Load balancer 320 may then send the packets to the appropriate processors 310 (act 830). Because processors 310 are arranged in a pipeline manner, load balancer 320 may send the packets to processor 310-1 regardless of whether the packets are intended for processor 310-1. Receiver 420 (FIG. 4) of processor 310-1 may receive the packets and determine whether the packets are intended for processor 310-1. To make this determination, receiver 420 may, for example, analyze the processor identifier and/or resource group identifier information associated with the packets. Receiver 420 may forward packets that are not intended for processor 310-1 to transmitter 430 via bypass path 440. Transmitter 430 may then output the packets to processor 310-2.

For packets intended for processor 310-1, receiver 420 may load balance the packets across resources 410 of the intended resource groups 412 (act 840). For example, receiver 420 may maintain information regarding the state of the individual resources 410 and assign packets to resources 410 based on this information.

Resources 410 may then process the packets (act 850). For independent packets (i.e., packets that require processing by only one resource 410), resources 410 may process the packets to completion. For dependent packets (i.e., packets that require processing by more than one resource 410), resources 410 may process the packets and then mark them with instructions for further processing by one or more additional resources 410 either within the same processor or a different processor.

When resources 410 complete processing, they forward the packets to transmitter 430 within the respective one of processors 310. Transmitter 430 may then output the packets to either the next one of processors 310 or reorder logic 330. Processed packets may pass through other processors 310 (via their bypass paths 440) to reorder logic 330.

Reorder logic 330 may reorder the packets to the order in which the packets were received by load balancer 320 (act 860). In particular, receiver 610 (FIG. 6), within reorder logic 330, may store the packets based on their assigned sequence numbers in buffer 620. Receiver 610 may also return state information to load balancer 320. For each received packet, receiver 610 may indicate that the corresponding resource group 412 and/or processor 310 (i.e., the one that processed the packet) is/are available for additional packet processing. As described above, load balancer 320 may use the state information in balancing the load given to resource groups 412 and/or processors 310.

Transmitter 630 may read the packets from buffer 620 based on their sequence numbers. Transmitter 630 may return the sequence numbers to load balancer 320 for reuse at the appropriate time. Transmitter 630 may also determine whether a packet is a dependent packet that requires processing by another one of resource groups 412. Transmitter 630 may make this determination based on instructions provided by the resource that processed the packet. These instructions may accompany the packets. When the packet is dependent, transmitter 630 may send the packet to load balancer 320 for distribution to the appropriate one of resource groups 412.

For packets that have completed processing, transmitter 630 may output them from system 300 in the order in which they were received by load balancer 320 (act 870).

Exemplary Multiple Pipeline System Overview

FIG. 9 is a block diagram illustrating an exemplary multiple pipeline packet processing system 900 consistent with the principles of the invention. System 900 may include processors 910-1 through 910-Z, where Z≧4 (collectively referred to as processors 910), connected in parallel pipelines (via buses 1-X) between load balancer 920 and reorder logic 930. Processors 910 and reorder logic 930 may be configured and operate similar to processors 310 and reorder logic 330, respectively, as described above with regard to FIGS. 3-8.

Load balancer 920 may be configured different from load balancer 320 to account for the multiple parallel processor pipelines. FIG. 10 is an exemplary diagram of load balancer 920 according to an implementation consistent with the principles of the invention. Load balancer 920 may include a classifier 1010, processing queues 1020-1 through 1020-S, where S≧2 (collectively referred to as queues 1020), resource group binding logic 1030, and bus binding logic 1040.

Classifier 1010 may include logic that processes received packets to identify which of processing queues 1020 to place the packets. Classifier 1010 may make this identification based on one or more fields in the packets. In other implementations, classifier 1010 may use other information in identifying queues 1020 to receive the packets. If classifier 1010 determines that a packet is dependent, then classifier 1010 may optionally place the packet in one of queues 1020 dedicated to dependent packets.

Processing queues 1020 may include buffers associated with different types of packets to be processed. In implementations consistent with the principles of the invention, queues 1020 may not directly relate to processors 910, but instead to the types of packets that processors 910 may process. For example, queues 1020 may include buffers for multicast packets, dependent packets, Ethernet packets, and ATM packets.

Resource binding logic 1030 may include logic that associates the packets in queues 1020 with resource groups 412 (FIG. 4) (labeled as resource groups RG1-RGT) of processors 910. Binding logic 1030 may include bindings from queues 1020 to resource groups RG1-RGT that identify resource groups 412 that are capable of processing the packets. For example, a binding may exist between queue 1020-1 and resource groups RG1 and RG2. This means that packets in queue 1020-1 may be sent to either resource group RG1 or resource group RG2. As described above, the resource groups may physically reside within one or more processors 910.

Binding logic 1030 may balance the distribution of packets across the associated resource groups. When a particular packet may be assigned to more than one resource group (e.g., a packet from queue 1020-3 may be assigned to resource group 3 or 4), binding logic 1030 may use state information in making its assignment. Binding logic 1030 may receive the state information from reorder logic 930.

Binding logic 1030 may send certain information along with packets that it outputs to processors 910. The information may be appended to the packets or sent in parallel with the packets. The information associated with a packet may include a processor identifier that identifies one of processors 910 to operate upon the packet. The information may also include a resource group identifier that identifies the particular resource group 412 to process the packet. The information may further include a sequence number that is used by reorder logic 930 to reorder packets that it receives to the order in which the packets were received by load balancer 920.

Bus binding logic 1040 may include logic that associates the resource groups 412 with the pipeline buses. Binding logic 1040 may include bindings from resource groups (RG1-RGT) to buses 1-X that include resource groups 412 that are capable of processing the packets. For example, binding logic 1030 and 1040 may ultimately provide a binding between queues 1020 and the pipeline buses.

With such a configuration, binding logic 1030 and 1040 may balance distribution of packets across the resource groups (RG1-RGT) and, thus, across buses 1-X. For example, binding logic 1030 and 1040 may balance distribution of packets from queue 4 to resource groups RG5 and RGT, thereby also balancing distribution of the packets to buses 1 and X.

CONCLUSION

Systems and methods consistent with principles of the invention provide a scalable packet processing architecture. With such a construction, the number of connections from the processors to the load balancer and reorder logic is reduced over conventional parallel processing architectures. The scalable packet processing architecture disclosed herein provides processors connected in a pipeline fashion that behave as if they were connected in parallel—thereby retaining the good properties of both pipeline and parallel processing systems.

The foregoing description of preferred embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention.

For example, the load balancer (320, 920) has been described as having knowledge of the resource groups (412) within each of the processors (310, 910). This need not be the case, however. In another implementation, the load balancer has no knowledge of the resource groups. In this case, the load balancer load balances packets over the processors, instead of balancing the load over the resource groups. In yet another implementation, the load balancer has knowledge of the resources (410) within each of the processors. In this case, the load balancer load balances packets over the individual resources.

Also, the packet processing systems of FIGS. 3 and 9 have been described as possibly being implemented within a network device. In another implementation consistent with the principles of the invention, each processor (310, 910) may include elements similar to those shown in FIGS. 3 and 9. In other words, each processor (310, 910) may include its own load balancer, set of sub-processors and/or resources, and reorder logic. Alternatively, each processor (310, 910) may not include reorder logic. In this case, there may be a single “system-level” reorder logic.

Further, a feedback mechanism has been described for transmitting packets from reorder logic (330, 930) to load balancer (320, 920). In another implementation consistent with the principles of the invention, a feedback mechanism may alternatively or additionally exist for transmitting packets from processors (310, 910) to load balancer (320, 920).

Certain portions of the invention have been described as “logic” that performs one or more functions. This logic may include hardware, such as an application specific integrated circuit, software, or a combination of hardware and software.

While a series of acts has been described with regard to the flowchart of FIG. 8, the order of the acts may differ in other implementations consistent with the principles of the invention. Further, non-dependent acts may be performed in parallel.

No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. The scope of the invention is defined by the claims and their equivalents. 

What is claimed is:
 1. A device comprising: a packet processor that includes: a receiver to receive a data unit, one or more resources, connected to the receiver, to process the data unit, a transmitter to receive, from the one or more resources, the processed data unit, and a redirect path directly connecting the transmitter to the receiver, the transmitter being further to: determine whether the processed data unit requires additional processing by the one or more resources, and return, via the redirect path, the processed data unit to the receiver when the processed data unit requires the additional processing.
 2. The device of claim 1, where the packet processor is one of a plurality of packet processors, and the packet processor is further to: determine that the data unit includes a first portion and a second portion, determine that the first portion is intended for the packet processor, process, via the one or more resources, the first portion, determine that the second portion is not intended for the packet processor, and forward, via a bypass path, the second portion to another packet processor, of the plurality of packet processors.
 3. The device of claim 2, further comprising: a reorder processor to: receive the processed first portion from the one or more resources, receive the processed second portion from the other packet processor, and combine the processed first portion and the processed second portion.
 4. The device of claim 1, where the packet processor is one of a plurality of packet processors, the data unit is included in a plurality of data units, and the device further comprises: a load balancer to distribute the plurality of data units among the plurality of packet processors.
 5. The device of claim 4, where the load balancer, when distributing the plurality of data units, is further to: organize the plurality of packet processors into two or more resource groups, and distribute sets of the plurality of data units among respective sets of the plurality of packet processors associated with the two or more resource groups.
 6. The device of claim 4, further comprising: a plurality of queues to store the plurality of data units, the load balancer, when distributing the plurality of data units, being further to: determine statuses of the plurality of queues, and distribute, based on the statuses of the plurality of queues, respective sets of the plurality of data units stored in the plurality of queues.
 7. The device of claim 4, where the load balancer, when distributing the plurality of data units, is further to: determine respective statuses of the plurality of packet processors, and distribute the plurality of data units based on the respective statuses of the plurality of packet processors.
 8. The device of claim 1, where the transmitter is further to: output the processed data unit to a destination when the processed data unit does not require the additional processing from the one or more resources.
 9. A method comprising: receiving, by a receiver included in a packet processor, a data unit; processing, by one or more resources included in the packet processor, the data unit; receiving, by a transmitter included in the packet processor, the processed data unit from the one or more resources; determining, by the transmitter, that the processed data unit, received from the one or more resources, requires additional processing by the one or more resources; and returning, by the transmitter and via a redirect path that connects the transmitter to the receiver, the processed data unit to the receiver for the additional processing by the one or more resources.
 10. The method of claim 9, where the packet processor is one of a plurality of packet processors, and the method further comprises: determining that the data unit includes a first portion and a second portion, and receiving, by the receiver, only the first portion of the data unit, the second portion being sent to another packet processor of the plurality of packet processors via a path that bypasses the packet processor.
 11. The method of claim 10, further comprising: receiving the processed first portion from the packet processor; receiving the processed second portion from the other packet processor; and combining the processed first portion and the processed second portion.
 12. The method of claim 9, where the packet processor is included in a plurality of packet processors, the data unit is included in a plurality of data units, and the method further comprises: distributing the plurality of data units among the plurality of packet processors.
 13. The method of claim 12, where, when distributing the plurality of data units, the method further comprises: organizing the plurality of packet processors into two or more resource groups, and distributing sets of the plurality of data units among respective sets of the plurality of packet processors associated with the two or more resource groups.
 14. The method of claim 12, further comprising: determining statuses of the plurality of packet processors; and distributing the plurality of data unit among the plurality of packet processors based on the determined statuses of the plurality of packet processors.
 15. The method of claim 9, further comprising: forwarding the processed data unit to a destination, external to the packet processor, after the additional processing by the one or more resources.
 16. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed by a transmitter, cause the transmitter to: receive a data unit from a resource for processing the data unit or from a receiver via a bypass path that excludes the resource, forward, when the data unit is received via the bypass path, the data unit to another processor, determine, when the data unit is received from the resource, whether to perform additional processing on the data unit received from the resource, return, via a redirect path, the data unit received from the resource to the receiver when the additional processing is to be performed by the resource, and forward, when the additional processing is not to be performed by the resource, the data unit received from the resource toward a destination.
 17. The non-transitory computer-readable medium of claim 16, where the receiver, the transmitter, and the resource are associated with a first packet processor, and the other processor is associated with a second packet processor that differs from the first packet processor.
 18. The non-transitory computer-readable medium of claim 17, where the data unit is included in two or more data units, and the instructions further comprise: one or more instructions to: determine respective statuses of the first packet processor and the second packet processor, and distribute, based on the respective statuses, the two or more data units among the first packet processor and the second packet processor.
 19. The non-transitory computer-readable medium of claim 16, where the data unit includes a first portion to be processed by the resource and a second portion to be processed by the other processor, and the instructions further comprise: one or more instructions to: forward the first portion of the data unit to the resource for processing, and forward, to the other processor, the second portion of the data unit.
 20. The non-transitory computer-readable medium of claim 19, where the instructions further comprise: one or more instructions to: receive the processed first portion from the resource, receive the processed second portion from the other processor, and combine the processed first portion and the processed second portion. 